Insulating glass units are well-known. They generally comprise at least two sheets of glass spaced from one another by a spacer element thereby providing a dead or insulating air space between the panes of glass. Many attempts have been made to hermetically seal insulating glass units so as to provide a barrier against air, dust, and water vapor. Typical methods used to seal insulating glass units are described in U.S. Letters Pat. Nos. 3,759,771 and 3,852,149.
The types of sealants previously used in preparing insulating glass units include sealants made from polysulfide materials which cure or crosslink at room temperature after application to the insulating glass unit. Such sealants provide adhesion of a chemical nature involving a chemical bond between glass, the metal spacing member and the sealant, generally brought about through a chemical intermediate.
Another type of sealant consists of uncrosslinked polymers such as butyl and polyisobutylene applied by hot-melt application. Hot-melt sealants, particularly those made from butyl rubber, plasticizers and fillers are useful insulating glass sealants since they possess inherently low water vapor transmission rates. Since hot-melt butyl sealants usually contain no solvents, shrinkage is minimal after these materials have been applied to an insulating glass unit and completely crosslinked or cured. Adhesion in such systems is usually of a physical nature employing the tacky properties of the butyl base polymers and any additives which contribute to tack. It is necessary, however, to apply mechanical banding about the periphery of insulating glass units sealed with this type of hot-melt sealant to prevent movement of the sealant due to creep, cold flow, stress or excessive temperature changes.
Another type of sealant comprises the application of uncrosslinked polymers in tape form or hot-melt form followed by the application of a second crosslinking sealant about the perimeter of the insulating glass unit to add structural strength. This type of sealant is particularly desirable since it provides both chemical and physical adhesion of the glass and spacer element making up the insulating glass unit. Further, in the event either of the sealants shall fail, the remaining sealant may be sufficient to maintain the integrity of the unit.
Regardless of the type of sealant used in forming the insulating glass unit, the function of the sealant is two-fold. First, the sealant is to provide and maintain the insulating glass unit in a hermetically sealed state and, second, the sealant should have adhesive properties which function to hold the glass panes and spacer element in a predetermined configuration.
An object of this invention is to provide an insulating glass unit and a method of fabricating insulating glass units with a single application sealant which will serve to hermetically seal the insulating glass unit and provide adhesive properties serving to maintain the insulating glass unit in a desired assembled configuration.
A further object is to provide a method for fabricating insulating glass units with a single application sealant having the advantages of ease of application and low water vapor transmission rates demonstrated by hot-melt sealants as well as the strong chemical adhesion and structural strength exhibited by most room temperature vulcanizing sealants.